80 lines
2.6 KiB
Python
Executable file
80 lines
2.6 KiB
Python
Executable file
#!/usr/bin/env python3
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#
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# create_metar_dat.py
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#
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# Script to create metar.dat.gz by checking weather.noaa.gov for stations
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# that have reported recently.
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#
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# Usage: create_metar_dat.py [OUTPUT_FILENAME]
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#
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# If OUTPUT_FILENAME is omitted, creates metar.dat.gz in working directory.
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#
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# Copyright (c) 2016 Richard Senior
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#
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# This program is free software; you can redistribute it and/or
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# modify it under the terms of the GNU General Public License
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# as published by the Free Software Foundation; either version 2
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# of the License, or (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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# MA 02110-1301, USA.
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import datetime
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import dateutil.parser
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import gzip
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import os
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import re
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import sys
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import urllib.request
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filename = "metar.dat.gz" if len(sys.argv) <= 1 else sys.argv[1]
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max_age_days = 7
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url = "http://weather.noaa.gov/pub/data/observations/metar/stations/"
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now = datetime.datetime.now()
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script = os.path.basename(__file__)
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class ParseException(Exception):
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pass
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def stations():
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for line in urllib.request.urlopen(url).readlines():
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if line.startswith(b"<img"):
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yield line
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def active_stations():
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cutoff = now - datetime.timedelta(max_age_days)
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icao_pattern = re.compile("[A-Z][A-Z0-9]{3}")
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for station in stations():
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tokens = station.split()
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last_modified = tokens[5]
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if dateutil.parser.parse(last_modified) > cutoff:
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icao = tokens[4][16:20:].decode()
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# Sanity check on parsed ICAO code.
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if not icao_pattern.match(icao):
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raise ParseException("Dubious ICAO code: " + icao)
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yield icao
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# Run through the active stations before opening the file so that a file
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# is not created (or overwritten) if an exception is thrown.
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active = [icao + "\n" for icao in active_stations()]
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# Sanity check on the number of stations.
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if len(active) < 5000:
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raise ParseException("Expected more than " + str(len(active)) + " stations")
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with gzip.open(filename, "wt") as f:
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print("# List of airports known to have metar data available", file=f)
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print("# Generated by", script, "on", now.strftime("%Y-%m-%d"), file=f)
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print("#", url, file=f)
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f.writelines(active)
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print(script + ": Wrote", len(active), "stations to", filename)
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